Sensors, Systems and Methods for Position Sensing

ABSTRACT

Various systems and methods for estimating the position of a radiation source in three-dimensional space, together with sensors for use in such systems are described. In some embodiments, the systems include a plurality of radiation sensors. The three-dimensional position of the radiation source is estimated relative to each sensor using an aperture that casts shadows on a radiation detector as a function of the incident angle of the incoming radiation. In some embodiments, the ratio of a reference radiation intensity to a measured radiation intensity is used to estimate direction of the radiation source relative to the sensor. When the angular position of the radiation source is estimated relative to two sensors, the position of the radiation source in three dimensions can be triangulated based on the known relative positions of the two sensors.

TECHNICAL FIELD

Embodiments described herein relate generally to apparatus andaccompanying methods for detecting the position of a radiation source inthree dimensions using angular position sensors and triangulationmethods.

BACKGROUND

Numerous industrial, commercial, scientific, gaming and otherapplications require sensing of the position of an object in two andthree dimensions. A variety of approaches exist for estimating theposition of an object. However, these approaches tend to have limitedaccuracy or a high cost, or both.

There is a need for apparatus, systems and method for detecting theposition of an object with increased accuracy compared to known methods.

SUMMARY OF EMBODIMENTS

A first aspect of the invention provides a sensor for estimating theangular direction of a radiation source relative to the sensor. Thesensor comprises: a reference radiation detector for providing areference radiation intensity signal corresponding to an intensity ofradiation incident on the reference radiation detector; a firstdirection radiation detector for providing a first direction radiationintensity signal corresponding to an intensity of radiation incident onthe first direction radiation detector; a second direction radiationdetector for providing a first direction radiation intensity signalcorresponding to an intensity of radiation incident on the seconddirection radiation detector; a radiation stop for partially blockingradiation from reaching the first and second direction radiationdetectors; and a processor coupled to the reference radiation detectorand to the first and second direction radiation detectors for providingfor providing first and second incident angles wherein the firstincident angle corresponds to the first direction radiation intensitysignal and the reference radiation intensity signal and the secondincident angle corresponds to the second direction radiation intensitysignal and the reference radiation intensity signal.

Another aspect provides a sensor for estimating the angular direction ofa radiation source relative to the sensor. The sensor comprises: areference radiation detector for providing a reference radiationintensity signal corresponding to an intensity of radiation incident onthe reference radiation detector; a first direction radiation detectorfor providing a first direction radiation intensity signal correspondingto an intensity of radiation incident on the first direction radiationdetector; a second direction radiation detector for providing a seconddirection radiation intensity signal corresponding to an intensity ofradiation incident on the second direction radiation detector; aradiation stop for partially blocking radiation from reaching the firstand second direction radiation detectors; and a processor coupled to thereference radiation detector and to the first and second directionradiation detectors for providing for providing first and secondincident angles wherein the first incident angle corresponds to thefirst direction radiation intensity signal and the reference radiationintensity signal and the second incident angle corresponds to the seconddirection radiation intensity signal and the reference radiationintensity signal.

Another aspect provides a sensor for estimating the angular direction ofa radiation source relative to the sensor, the sensor comprising: areference radiation detector for providing a reference radiationintensity signal corresponding to an intensity of radiation incident onthe reference radiation detector; a pair of first direction radiationdetector for providing a pair of first direction radiation intensitysignal corresponding to an intensity of radiation incident on the firstdirection radiation detector; a pair of second direction radiationdetector for providing a pair second direction radiation intensitysignal corresponding to an intensity of radiation incident on the seconddirection radiation detector; a radiation stop for partially blockingradiation from reaching the first and second direction radiationdetectors; and a processor coupled to the reference radiation detectorand to the first and second direction radiation detectors for providingfor providing first and second incident angles wherein the firstincident angle corresponds to the first direction radiation intensitysignals and the reference radiation intensity signal and the secondincident angle corresponds to the second direction radiation intensitysignals and the reference radiation intensity signal.

Another aspect provides a sensor for estimating the angular direction ofa radiation source relative to the sensor, the sensor comprising: areference radiation detector for providing a reference radiationintensity signal corresponding to an intensity of radiation incident onthe reference radiation detector; a pair of directional radiationdetector for providing a pair of directional radiation intensity signalcorresponding to an intensity of radiation incident on the firstdirection radiation detector; a radiation stop for partially blockingradiation from reaching the first and second direction radiationdetectors; and a processor coupled to the reference radiation detectorand to the directional radiation detectors for providing for providingan incident angle, wherein the incident angle corresponds to thedirectional radiation intensity signals and the reference radiationintensity signal.

Another aspect provides a sensor for estimating the angular direction ofa radiation source relative to the sensor. The sensor comprises: a pixelarray detector having an array of a pixels sensitive to radiation; anaperture plate having an aperture, wherein the aperture plate isarranged relative to the pixel array detector to partially blockingradiation from reaching the pixel array detector; a processor coupled tothe pixel array detector to receive radiation intensity informationrelating to the intensity of radiation incident on the pixels of thepixel array detector, wherein the processor is adapted to provide firstand second incident angles, wherein the first incident angle iscorresponds to the position of one or more pixels having a relativelyhigh level of incident radiation in a first direction and the secondincident angle corresponds to the position of one or more pixels have arelatively high level of incident radiation in a second direction.

Another aspect provides a system for estimating the position of aradiation source in three dimensional space. The system comprises: afirst radiation sensor for receiving radiation from the radiation sourceand for providing a first incident angle pair corresponding to thedirection of the radiation source relative to the first radiationsource; a second radiation sensor for receiving radiation from theradiation source and for providing a second incident angle paircorresponding the direction of the radiation source relative to thesecond radiation source; and a processor for calculating the estimatedposition of the radiation source based on the first and second incidentangle pairs.

In some embodiments, the processor is adapted to calculate the estimatedposition of the radiation source by determining a point of intersectionbetween a first line defined by the first incident angle pair and theposition of the first radiation sensor and a second line defined by thesecond incident angle pair and the second radiation sensor.

In some embodiments, the processor is adapted to calculate the estimatedposition of the radiation source by identifying a line segment betweenthe closest points between a first line defined by the first incidentangle pair and the position of the first radiation sensor and a secondline defined by the second incident angle pair and the second radiationsensor.

In some embodiments, the processor is adapted to calculate the estimateposition of the radiation source by bisecting the line segment.

In some embodiments, the first and second sensors are mounted in a fixedrelationship to one another.

In some embodiments, the first and second sensors may be independentlypositioned relative to one another.

Another aspect provides a method of estimating the position of aradiation source. The method comprises: positioning first and secondsensors in a three dimensional space, wherein the first second sensorare separated by a sensor spacing distance; calculating a first linecorresponding to the position of the first sensor and the position ofthe radiation source; calculating a second line corresponding to theposition of the second sensor and the position of the radiation source;and calculating an estimated position of the radiation source based onthe first and second lines.

In some embodiments, the method includes estimating the position of theradiation source by identifying a point of intersection between thefirst and second lines.

In some embodiments, the method includes estimating the position of theradiation source by identifying a line segment between the closestpoints on the first and second lines.

In some embodiments, the method includes estimating the position of theradiation source by bisecting the line segment.

These and other aspect of the present invention are further describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments are described in further detail below, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 a is a top view of a first sensor according to the invention;

FIGS. 1 b and 1 c are side views of the sensor of FIG. 1 a;

FIG. 2 a is a top view of another sensor according to the invention;

FIGS. 2 a and 2 b are side views of the sensor of FIG. 2 a;

FIG. 3 is a top view of a three-dimensional optical position sensingsystem;

FIG. 4 is a top view of another three-dimensional optical positionsensing system;

FIG. 5 illustrates the use of a three-dimensional optical positionsensing system to estimate the position of a radiation source;

FIG. 6 is another illustration of a the use of a three-dimensionaloptical position sensing system to estimate the position of a radiationsource;

FIG. 7 is a flow chart of a method for estimating the position of anobject in three space;

FIG. 8 is a top view of another sensor according to the invention; and

FIG. 9 is a top view of another sensor according to the invention.

The figures are illustrative only and are not drawn to scale.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Example embodiments described herein provide details relating to opticalsensor systems and methods for determining the position of a radiationsource relative to the position of one or more sensors. The radiatingsource may radiate in the visible light spectrum, but it may alsoradiate in other light spectrums, such as the ultraviolet or infraredlight spectrums. The optical sensors comprise solid-state radiationdetectors. The radiation source may be an active radiation source thatgenerates radiation, such as a light bulb, LED or other radiationemitting element. The radiation source may be a passive radiation sourcethat reflects radiation from another source or sources. Otherimplementations and configurations of optical sensors are also possiblewithin the scope of the invention. The embodiments described herein areexamples only.

Reference in now made to FIGS. 1 a-1 c, which illustrate a first exampleoptical sensor 100. A radiation source 110 is positioned relative tosensor 100 such that radiation from the radiation source 110 is incidentupon the sensor 100.

Sensor 100 comprises reference radiation detector 102, first directionradiation detector 104, second direction radiation detector 106,aperture plate 108, a mounting substrate 112 and a processor 120.

Mounting substrate 112 is substantially parallel to an x-y plane. Thereference detector 102, first direction detector 104 and seconddirection detector 106 are mounted to the mounting substrate 112.Aperture plate 108 is positioned between the detectors 102-106 and theradiation source 110 in a z-dimension, which is orthogonal to the x-yplane. The aperture plate may also be referred to as a radiation stop orradiation block.

Incoming radiation from radiation source 110 striking sensor 100 impactsupon first direction radiation detector 104 at incident angle θ relativeto the x-axis, and upon second direction radiation detector 106 atincident angle φ relative to the y-axis. The incident angle pair (θ, φ)defines an angular position of radiation source 110 relative to sensor100.

Sensor 100 estimates incident angle pair (θ, φ) using reference detector102 and aperture plate 108 in conjunction with first and seconddirection radiation detectors 104, 106. Aperture plate 108 is arrangedat height H, relative to first and second direction radiation detectors104, 106.

Aperture plate 108 is disposed such that it overlies both first andsecond positions detectors 104,106. In this example, first and seconddirection detectors 104,106 are mounted onto mounting substrate 112 suchthat an edge of aperture plate 108 will approximately align with acenterline of each direction detector 104, 106. Reference detector 102is mounted onto mounting substrate 112 such that no overlap (in the x ory dimensions) is created between it and aperture plate 108. Mountingsubstrate 102 may be constructed from any suitable material to supportthe detectors 102, 104 and 106. Detectors 102, 104 and 106 receive powerfrom a power supply (not shown) and provide electronic signals toprocessor 120. In some embodiments, mounting substrate 102 may be asemiconductor material such as a printed circuit board (PCB) thatincludes conductors to couple the detectors to the power supply andprocessor 120. Optionally, aperture plate 108 may be mounted to themounting substrate 112 or it may be mounted to another support thatholds it in a relatively fixed position relative to detectors 102, 104and 106.

In this embodiment, reference detector 102, and direction detectors104,106 are implemented for example as solid-state radiation detectors.Other types of radiation detectors may also be used. Aperture plate 108is constructed for example out of a suitable opaque material such thatincoming radiation from radiation source 110 is substantially absorbedor reflected. Other implementations of sensor 100 are possible.

When incoming radiation from radiation source 110 strikes sensor 100,reference detector 102 will be fully exposed to the incoming radiation.The radiation intensity detected by reference detector 102 forms areference radiation intensity that is a measure of radiation fromradiation source 110 and ambient conditions. In contrast, first andsecond direction radiation detectors 104, 106 will, through theiroverlie with aperture plate 108, not be fully exposed to the incomingradiation, and thus will receive an intensity of incoming radiation fromradiation source 110 that is in generally not equal to the intensityreceived by exposed reference detector 102. The different radiationintensities received by positions sensors 104, 106, relative toreference detector 102, can be used to estimate the angular position ofradiation source 110, relative to sensor 100.

FIG. 1 b shows incident radiation striking first direction radiationdetector 104 at an incident angle θ relative to the x-axis. Dimension s₁defines the part of first direction detector 104 that lies in the shadowcreated by aperture plate 108, from the centerline 114 of the detector.Likewise dimension d₁ defines the part of first direction detector 104,relative to centerline 114, that is exposed to incoming radiation fromradiation source 110. For positive incident angle θ, the part ofposition sensor on the other side of centerline 114 is covered in shadowas well. Dimension s₁ and d₁ are related to width D of first directiondetector 102 according to,

$\begin{matrix}{s_{1} = {\frac{D}{2} - {d_{1}.}}} & \left( {{Equation}\mspace{14mu} 1} \right)\end{matrix}$

For an incident angle of about 90 degrees, about half of directiondetector 102 will be covered in shadow (i.e. s₁ is approximately equalto zero) More generally, incident angle θ of radiation source 110 isrelated to dimension s₁ and height H according to:

$\begin{matrix}{{\tan \; \theta} = {\frac{H}{s_{1}}.}} & \left( {{Equation}\mspace{14mu} 2} \right)\end{matrix}$

Reference detector 102 and direction detector 104 are coupled toprocessor 120. Both reference detector 102 and direction detector 104provide radiation intensity signals f that are generally proportional tothe intensity of radiation sensed by the respective detector. Processor120 is adapted to use these radiation intensity signals to estimate theposition of radiation source 110 relative to the sensor 100.

Reference detector 102 provides a baseline intensity signal f_(m)against which other radiation intensity levels may be compared. Forexample, detector 104, which through its overlie with aperture plate 108is only partially exposed to radiation source 110. Ray 128 illustratesthe ray of radiation at the boundary between the illuminated andshadowed regions of detector 104. Ray 128 is illustrated partly in abroken line to indicate that typically radiation source 110 will be muchfurther from sensor 100 compared to the dimensions of the sensor.Typically, the distance between the radiation source and the sensor willbe one or more orders of magnitude greater than the dimensions of thesensors.

Radiation detector 104 provides a radiation intensity signal f₁ wheregenerally f₁<f_(m). The ratio of radiation intensity f₁ relative toreference radiation intensity f_(m) provides a measure of the ratiobetween shadow region S and exposed region d₁, and is given by,

$\begin{matrix}{{\frac{f_{1}}{f_{m}} = {{\alpha \frac{d_{1}}{D}} + \beta}},} & \left( {{Equation}\mspace{14mu} 3} \right)\end{matrix}$

where α models a gain factor and β models an offset factor introducedthrough practical implementations of reference detector 102 and firstdirection detector 104. In some implementations, the gain factor α maybe approximately equal to one, and offset factor β may be approximatelyequal to zero. In practical implementations, radiation detectors willtypically exhibit offsets and non-linearities that may be modeled withthese corrective factors. Offset factor β may be used to compensate forambient radiation.

In various embodiments of the invention, α, β and other correctivefactors may be used to model the operating characteristics of thesensors. For example, in sensor 100, detectors 102, 104, 106 are squareshaped with width and length D. In other embodiments, the sensors mayshaped differently. It is not necessary that sensors 102, 104 and 106 beidentical sensors. In various embodiments, different sensors may be usedfor the reference sensor and the direction sensors and in otherembodiments, different direction sensors may be different. Additionalcorrective factors may be used to scale or otherwise adjust the outputsof the various sensors to allow the direction of the radiation source tobe estimated.

Returning to the present exemplary embodiment, combining equations 1, 2and 3 yields an overall expression for incident angle θ of radiationsource 110 and is given by:

$\begin{matrix}{\theta = {{\tan^{- 1}\left( \frac{H}{\frac{D}{2} - {\left( {\frac{f_{1}}{f_{m}} - \beta} \right)\frac{D}{\alpha}}} \right)}.}} & \left( {{Equation}\mspace{14mu} 4} \right)\end{matrix}$

Width D and height H are known parameters, while gain factor α andoffset factor β may be determined experimentally, if they are used atall. The ratio of f₁ to f_(m) is computed based upon the output signalsof reference detector 102 and first direction detector 104.

Referring to FIG. 1 c, radiation detector 106 is partially illuminatedby radiation source 110 to a distance S₂ from its centerline 116. Theincident angle φ of radiation source 110 relative to the y-axis, asshown in FIG. 3 b, is given by

$\begin{matrix}{{\varphi = {\tan^{- 1}\left( \frac{H}{\frac{D}{2} - {\left( {\frac{f_{2}}{f_{m}} - \beta} \right)\frac{D}{\alpha}}} \right)}},} & \left( {{Equation}\mspace{14mu} 5} \right)\end{matrix}$

where f₂ is the radiation intensity signal provided by second directiondetector 106. In this example, incident angle φ is a negative angle.

Incident angle pair (θ, φ) of radiation source 110 is an estimate of thedirection of radiation source 110 relative to the sensor 100.

Processor 120 is adapted to receive the radiation intensity signalsf_(m), f₁ and f₂ and to calculate incident angle pair (θ, φ). Processor120 may implement the mathematical formulae set out above or mayimplement corresponding calculations and in some cases may usemathematical techniques that provide an estimate of the results of theformulae. For example, the processor may use look up tables, small angleapproximations and other tools to estimate the incident angle pair. Insome systems utilizing sensor 100, it may not be necessary to calculateangles θ and φ directly. For example, in some systems, the value oftan(θ) and tan(φ) could be used without calculating the anglesthemselves. In such cases, the processor may be adapted to calculatethese values without then calculating the angles.

In this embodiment, processor 120 is a microprocessor and is adapted tocarry out additional functions beyond those described herein. The term“processor” is not limited to any particular type of data processing orcalculating element. In various embodiments, the processor may be amicrocontroller, a microprocessor, a programmed logic controller such asa floating point gate array or any other suitable device capable ofcalculation. The processor may operate in conjunction with additionalelements such as a power supply, data storage elements, input/outputdevices and other devices.

Aperture plate 108 may optionally be adapted to reduce non-linearitiesin the length of the shadow cast by the aperture plate on detectors 104and 106 when radiation source 110 passes over their respectivecenterlines 114 and 116. In the present embodiment, the edge of apertureplate 108 is beveled to reduce the effect of the thickness of theaperture plate 108 on the shadow. In other embodiments, the edge of theaperture plate may be rounded. In other embodiments, the aperture platemay additionally or alternatively be made from a thin material to reduceits effect on the shadow. In some embodiments, processor 102 may beadapted to compensate for non-linearities in the position of the shadowcast by the aperture plate. For example, such non-linearities may bemodeled into the formulae or look-up tables used by the processor toestimate the incident angle pair (θ, φ).

Reference is now made to FIGS. 2 a-2 c, which illustrate another sensor200 according to the present invention. Some elements of sensor 200 aresimilar to elements of sensor 100 and corresponding elements areidentified by similar reference numerals. FIG. 2 a is a top-view ofsensor 200 in an x-y plane. FIG. 2 b illustrates a cross-sectional viewof sensor 200 in an x-z plane, while FIG. 2 c likewise illustrates across-sectional view of detector 200 along in a corresponding y-z plane.Detector 200 comprises a pixel-array detector 202, aperture plate 208,mounting substrate 212 and processor 220.

Aperture plate 208 is arranged at height H relative to detector 202 andis positioned so as to overlie with detector 202 in both the x and ydirections. Aperture plate 208 plate has an aperture 206, which in thisembodiment is centered above detector 202. Aperture plate 208 isgenerally parallel to detector 202.

A portion of incoming radiation from a radiation source 210 strikingdetector 200 passes through aperture 206 and impacts upon detector 202at incident angle θ relative to the x-axis and incident angle φ relativeto the y-axis. The incident angle pair (θ, φ) defines an angularposition of radiation source 210 relative to detector 200. Pixel-arraydetector 202 has an array of radiation-sensitive pixels arranged in rowsparallel to the x-axis and columns parallel to the y-axis.

In this embodiment, aperture 206 is circular. In other embodiments, theaperture may have another shape. For example, the aperture may be squareor rectangular with its edges generally parallel to the x and y axes.The aperture may be square with its edges arranged at an angle (such asa 45 degree) angle to the x and y axes. Other shapes may also be used.

In various embodiments, the pixel-array detector may be a CCD detector,a CMOS detector or other type of radiation sensitive detector. Processor220 is coupled to the pixel-array detector to periodically determinewhich pixels are illuminated by radiation source 2 10. This may done ina variety of ways. For example, detector 202 may be adapted to output adata stream indicating the illumination intensity of each of its pixelssequentially; processor 220 may be adapted to query the detector 202 toobtain the illumination intensity for each pixel or for some of thepixels in detector 202.

When incoming radiation from radiation source 210 strikes detector 202,pixels that are exposed to the radiation will have a high illuminationintensity while pixels located in the shadow cast by aperture plate 208will have a low illumination intensity. The positions of pixels with ahigh illumination intensity may be used to estimate incident angle pair(θ, φ).

FIG. 2 b shows incident radiation striking detector 202 at an incidentangle θ relative to the x-axis. A range of pixels s₁ in a row of thedetector 202 is illuminated by the incident radiation through aperture206.

Processor 220 is configured to identify the row of pixels with thewidest range of illuminated pixels, which will typically correspond tothe diameter of aperture 202 parallel to the x axis. Processor 220identifies a center x-dimension pixel p₁ at or near the center of therange of pixels s₁ within the identified row. Pixel p₁ is spaced adistance d₁ from a reference point 222.

Distance d₁ may be determined based on the dimensions and arrangement ofpixels in detector 202, or a lookup table or other method may be used todetermine the distance d₁ corresponding to pixel p_(i). In this example,reference point 222 is at an edge of detector 202. In other embodiments,the reference point may be at another position on the x-y plane of thesurface of detector 202.

When radiation source 210 is directly above sensor 200, a range ofpixels S_(c) is illuminated and a center pixel P_(c) is at or near thecenter of pixel range S_(c). Pixel P_(c) is spaced a distance D_(c) fromreference point 222.

Incident angle θ may be calculated as:

$\begin{matrix}{\theta = {{\tan^{- 1}\left( \frac{d_{1} - D_{c}}{H} \right)}.}} & \;\end{matrix}$

Typically, the values of D_(c) and H will be recorded in processor 220.Processor 220 repeatedly obtains pixel illumination information fromdetector 202 and identifies a center pixel p₁ and estimates angle θ asradiation source 210 moves relative to sensor 200.

As with processor 120, processor 220 may be adapted to implement theformulae described above or may be implement corresponding calculationsor use other methods to estimate angle θ.

Referring to FIG. 2 c, radiation source 210 illuminates a range ofpixels s₂ in a column of pixels parallel to the y-axis of detector 202.A distance d₂ is determined based on the center pixel p₂ in the range ofpixels s₂ and incident angle φ is calculated as:

$\varphi = {{\tan^{- 1}\left( \frac{d_{2} - D_{c}}{H} \right)}.}$

The incident angle pair (θ, φ) provide an estimate of the direction ofillumination source 210 relative to the position of sensor 200.

In FIGS. 2 a and 2 b, radiation from radiation source 210 that passessthrough aperture 206 is illustrated having parallel edges. Typically,most radiation sources will divergent radiation output. In mostembodiments, the divergence of the radiation may be ignored. Forexample, in many embodiments, the distance between radiation source 210and aperture plate 208 will substantially exceed the distance betweenaperture plate 208 and sensor 202 be several orders of magnitude or moreand the divergence of the will be negligible in comparison to thedimensions of the radiation reaching sensor 202. In some embodiments,processor 220 may optionally be adapted to compensate for the divergenceof the radiation using various geometric and computational operations.

Reference is now made to FIG. 3, which illustrates a three dimensionaloptical position sensing system 300. System 300 comprises two sensors332, 334, each of which is similar to sensor 100 (FIG. 1 a). In thisembodiment, the two sensors share a common aperture plate 308 which hasan aperture formed in it for each of the respective sensors. Sensors 332and 334 also share a common mounting substrate 312, which holds them ina fixed relationship to one another. Sensors 332 and 334 also share aprocessor 320 which communicates with each of the detectors in each ofthe sensors.

Sensors 332, 334 are disposed along an x-axis and are separated bydistance W. Processor 320, which is part of each sensor 332,334determines an angular position for radiation source, in terms ofincident angle pair (θ, φ). For example, sensor 332 determines anestimated incident angle pair (θ, φ), while sensor 334 determines anestimated incident angle pair (θ₂, φ₂). Each estimated incident anglepair (θ, φ) defines the direction of radiation source 310 relative tothe respective sensor 332 or 334.

Referring next to FIG. 4, another three dimensional optical positionsensing system 400 is illustrated. System 400 has a pair of sensors 432and 434 similar to sensor 200 (FIG. 2). In this embodiment, sensors 432and 434 share a common processor 420. Processor 420 is coupled to eachthe pixel-array detector in sensor. In this embodiment, processor 420,like the detector 402 of sensor 432 is mounted to the substrate 412 ofsensor 402 and communicates with that detector through conductors in themounting substrate. Processor 420 communicates with the detector ofsensor 434 through wire 436. In other embodiments, processor 420 maycommunicate with sensor 434 through a wireless communication system.

Sensors 432 and 434 have independent mounting substrates (not shown inFIG. 4) and aperture plates 408, allowing them to be moved independentlyand space apart by a variable distance W. Alternatively, sensors 432 and434 may be mounted to a common mounting substrate which would hold themin fixed relation to one another.

Referring briefly to FIG. 3, sensors 332 and 334 could alternatively bemounted to independent mounting substrates and have independent apertureplates, allowing them to be moved independently of one another. Theycould continue to share a processor which could be coupled to detectorsin one or both of the sensor through by wires or wirelessly.

Reference is now made to FIG. 5, which illustrates the use of multiplesensors to estimate the position of a radiation source 510 in threedimensional space using a pair of sensors 532 and 534. Triangulating theposition of an object in three-space requires at least two referencepoints A,B and two lines 542, 544, wherein reference points A, B definea third line segment. FIG. 5 is a top view of the arrangement of sensors532, 534 and radiation source 510. Lines 542 and 544 extend throughtheir respective sensors in three-dimensional space and are notnecessarily co-planar.

Reference point A in FIG. 5. is the position of sensor 532. Referencepoint B is the position of sensor 534. Sensor 532 calculates a firstincident angle pair (θ₁, φ₁) that estimates the direction of radiationsource 510 relative to sensor 532. Incident angle pair (θ₁, φ₁) areillustrated at line 542.

Similarly, sensor 534 calculates a second incident angle pair (θ₂, φ₂)that corresponds to line 544 as an estimate of the direction of theradiation source relative to sensor 534. Sensors 532 and 534 share aprocessor that is adapted to find the intersection point 548 of lines542 and 544, which is an estimate of the position of radiation source510. Lines 542 and 544 are practically only estimates of the directionof radiation source relative to each sensor and accordingly will notintersect is some cases.

Reference is next made to FIG. 6, in which a more practical approach toestimating the position is illustrated using a pair of sensors 632 and634. Lines 642 and 644 are respectively estimates of the direction ofradiation source 610 from each of the sensors 632 and 634. Processor 620is coupled to each of the sensors to estimate lines 642 and 644 in theform of incident angle pairs that originate at the sensors 632 and 634.Lines 642 and 644 extend in three dimensional space. Using standardmathematical techniques a line segment 646 the terminates at the closestpoints on lines 642 and 644 may be calculated. Processor 620 isprogrammed to calculate this shortest line segment 646 between lines 642and 644. Processor 620 then bisects the line segment 646 to calculatepoint 648, which is an estimate of the position of radiation source 610.

Reference is next made to FIG. 7, which illustrates a method 700implemented in processor 620 to calculate point 648.

Method 700 begins in step 702, in which a pair of sensors are positionedin a three dimensional space. The pair of sensors may be any type ofsensors that are capable of estimating a direction of radiation sourcerelative to each of the sensors. For example, the two sensor may besensors 332 and 334 (FIG. 3) or sensors 432 and 434 (FIG. 4) or sensors532 and 534 (FIG. 5) or sensors 632 and 634 (FIG. 6). The remainder ofthis method will be explained as an example with reference to FIG. 6,although any suitable sensor may be used in the method. The sensors arepositioned such that a radiation source (such as radiation source iswithin the field of view of each of the sensors and have a distance Wbetween them.

Method 700 then proceeds to step 704, in which a first line iscalculated in terms of a first reference point and a first incidentangle pair (θ, φ) defining an angular position in three-space. Forexample, the first line segment may be line 642, which has a referencepoint at the location of sensor 632 and extends in direction defined byfirst incident angle pair (θ₁, φ₁).

Method 700 then proceeds to step 706 in which a second line iscalculated in terms of a second reference point and a second incidentangle pair (θ, φ) is calculated. In this example, the second referencepoint is the position of sensor 634 and the second line is line 644,which extend from sensor 634 in a direction defined by second incidentangle pair (θ₂, φ₂).

Method 700 then proceeds to step 708 in which a line segment connectingthe two closest points between the first and second line is calculated.In FIG. 6, the closest points on lines 642 and 644 are points 652 and654. These point are identified as the endpoints of the shortest linesegment 646 between lines 642 and 644. In the event that lines 642 and644 intersect (i.e. the shortest line segment is of zero length), thepoint of intersection is deemed to be point 648 and the method ends.

If lines 642 and 644 do not intersect, method 700 proceeds to step 710in which line segment 644 is bisected to find point 648 and the methodends.

Point 648 is an estimate of the position of the radiation source 610 inthe three dimensions space in which the radiation sources arepositioned.

Reference is next made to FIG. 8, which illustrates another examplesensor 800 according to the present invention. Sensor 800 is similar invarious aspects to sensor 100 and similar elements are identified withsimilar reference numerals.

Sensor 800 includes a reference radiation detector 802, a pair of firstdirection radiation detectors 804 a and 804 b, a pair of seconddirection radiation detectors 806 a and 806 b, an aperture plate 608, amounting substrate 812 and a processor 820.

Mounting substrate is substantially parallel to an x-y plane. Thereference detector 802, first direction detectors 804 and seconddirection detectors 806 are mounted to the mounting substrate. Apertureplate 808 is positioned between the detectors 802, 804, 806 and aradiation source 810 in a z-dimension, which is orthogonal to the x-yplane.

Aperture plate 808 has a square aperture 824 formed in it and detectors802, 804 a and 804 c are positioned relative to the aperture 824 suchthat they are illuminated by a radiation source 810 in the same manneras a detectors 802, 804 and 806 of sensor 100 (FIG. 1). An edge 826 ofthe aperture 808 is aligned with the y direction centerline of detector804 b such that detectors 804 a and 804 b are typically illuminated in asimilar way by radiation source 810. The distance between detectors 604a and 604 b may result in radiation from radiation source 810 reachingdetectors 804 a and 804 b at slightly different angles. Typically, thedimensions of sensor 800 will be significantly smaller than the distancebetween radiation source and the sensor 800 and this small differencecan neglected. In some embodiments, this difference may be compensatedfor by processor 820.

Processor 820 is coupled to each of the detectors through conductorswithin the mounting substrate 812. Processor 820 receives a pair ofradiation intensity signals f_(1a) and f_(1b) from detectors 804 a and804 b. Processor 820 averages the two radiation intensity signals tocalculate an average radiation intensity f₁, which is then used estimatean angle θ (not shown in FIG. 8) at which radiation from radiationsource 810 strikes sensor 800 as described above in relation to sensor100 (FIG. 1) relative to the x dimension.

Similarly, processor 820 receives a pair of radiation intensity signalsf_(2a) and f_(2b) which are averaged and combined with a referenceintensity signal f_(m) from detector 802 to estimate an angle φ (notshown in FIG. 1) at which radiation from radiation source 810 strikessensor 800 relative to the y-dimension.

The incident angle pair (θ, φ) collectively form an estimate of theangle radiation source 810 relative to the sensor 800.

In this example, first direction radiation detectors 804 a and 804 b areequally spaced from reference radiation detector 802 and similarlysecond direction radiation detectors 806 a and 806 b are equally spacedfrom reference radiation detector 802. In other embodiments, a pair ofdirection radiation detectors may be unequally spaced from the referenceradiation detector. Optionally, in such embodiments, the processor mayapply a differential weighting to the radiation intensity signalsreceived from the two direction radiation detectors (instead of simplyaveraging the radiation intensity signals) to compensate for thedifferent distances between the direction radiation detectors and thatreference radiation detectors.

Reference is next made to FIG. 9, which illustrates a single directionsensor 900 that is based on sensor 800. Corresponding components of thetwo sensors are identified with similar reference numerals. Sensor 900has a reference radiation detector 902 and a single pair of directionradiation detectors 904 a and 904 b. Radiation detectors 904 a and 904 boperate in the same manner as radiation detectors 804 a and 804 b (FIG.8) to provide a pair of radiation intensity signal f1 a and f1 b toprocessor 920. Processor 920 averages signal f_(1a) and f_(1b) andcompares the average radiation intensity f₁ with a reference radiationintensity signal f_(m) from detector 902 to provide a signal incidentangle θ, which is an estimate of the direction of radiation source 910relative to sensor 900 in one dimension. Sensor 900 may be used inembodiment in which it is desirable to estimate the position of theradiation source in one angular dimension.

Various examples of the present invention have been described. Theseexamples do not limit the scope of the present invention.

1. A sensor for estimating the angular direction of a radiation sourcerelative to the sensor, the sensor comprising: a reference radiationdetector for providing a reference radiation intensity signalcorresponding to an intensity of radiation incident on the referenceradiation detector; a first direction radiation detector for providing afirst direction radiation intensity signal corresponding to an intensityof radiation incident on the first direction radiation detector; asecond direction radiation detector for providing a first directionradiation intensity signal corresponding to an intensity of radiationincident on the second direction radiation detector; a radiation stopfor partially blocking radiation from reaching the first and seconddirection radiation detectors; and a processor coupled to the referenceradiation detector and to the first and second direction radiationdetectors for providing for providing first and second incident angleswherein the first incident angle corresponds to the first directionradiation intensity signal and the reference radiation intensity signaland the second incident angle corresponds to the second directionradiation intensity signal and the reference radiation intensity signal.2. A sensor for estimating the angular direction of a radiation sourcerelative to the sensor, the sensor comprising: a reference radiationdetector for providing a reference radiation intensity signalcorresponding to an intensity of radiation incident on the referenceradiation detector; a first direction radiation detector for providing afirst direction radiation intensity signal corresponding to an intensityof radiation incident on the first direction radiation detector; asecond direction radiation detector for providing a second directionradiation intensity signal corresponding to an intensity of radiationincident on the second direction radiation detector; a radiation stopfor partially blocking radiation from reaching the first and seconddirection radiation detectors; and a processor coupled to the referenceradiation detector and to the first and second direction radiationdetectors for providing for providing first and second incident angleswherein the first incident angle corresponds to the first directionradiation intensity signal and the reference radiation intensity signaland the second incident angle corresponds to the second directionradiation intensity signal and the reference radiation intensity signal.3. A sensor for estimating the angular direction of a radiation sourcerelative to the sensor, the sensor comprising: a reference radiationdetector for providing a reference radiation intensity signalcorresponding to an intensity of radiation incident on the referenceradiation detector; a pair of first direction radiation detector forproviding a pair of first direction radiation intensity signalcorresponding to an intensity of radiation incident on the firstdirection radiation detector; a pair of second direction radiationdetector for providing a pair second direction radiation intensitysignal corresponding to an intensity of radiation incident on the seconddirection radiation detector; a radiation stop for partially blockingradiation from reaching the first and second direction radiationdetectors; and a processor coupled to the reference radiation detectorand to the first and second direction radiation detectors for providingfor providing first and second incident angles wherein the firstincident angle corresponds to the first direction radiation intensitysignals and the reference radiation intensity signal and the secondincident angle corresponds to the second direction radiation intensitysignals and the reference radiation intensity signal.
 4. A sensor forestimating the angular direction of a radiation source relative to thesensor, the sensor comprising: a reference radiation detector forproviding a reference radiation intensity signal corresponding to anintensity of radiation incident on the reference radiation detector; apair of directional radiation detector for providing a pair ofdirectional radiation intensity signal corresponding to an intensity ofradiation incident on the first direction radiation detector; aradiation stop for partially blocking radiation from reaching the firstand second direction radiation detectors; and a processor coupled to thereference radiation detector and to the directional radiation detectorsfor providing for providing an incident angle, wherein the incidentangle corresponds to the directional radiation intensity signals and thereference radiation intensity signal.
 5. A sensor for estimating theangular direction of a radiation source relative to the sensor, thesensor comprising: a pixel array detector having an array of a pixelssensitive to radiation; an aperture plate having an aperture, whereinthe aperture plate is arranged relative to the pixel array detector topartially blocking radiation from reaching the pixel array detector; anda processor coupled to the pixel array detector to receive radiationintensity information relating to the intensity of radiation incident onthe pixels of the pixel array detector, wherein the processor is adaptedto provide first and second incident angles, wherein the first incidentangle is corresponds to the position of one or more pixels having arelatively high level of incident radiation in a first direction and thesecond incident angle corresponds to the position of one or more pixelshave a relatively high level of incident radiation in a seconddirection.
 6. A system for estimating the position of a radiation sourcein three dimensional space, the system comprising: a first radiationsensor for receiving radiation from the radiation source and forproviding a first incident angle pair corresponding to the direction ofthe radiation source relative to the first radiation source; a secondradiation sensor for receiving radiation from the radiation source andfor providing a second incident angle pair corresponding the directionof the radiation source relative to the second radiation source; and aprocessor for calculating the estimated position of the radiation sourcebased on the first and second incident angle pairs.
 7. The system ofclaim 6 wherein the processor is adapted to calculate the estimatedposition of the radiation source by determining a point of intersectionbetween a first line defined by the first incident angle pair and theposition of the first radiation sensor and a second line defined by thesecond incident angle pair and the second radiation sensor.
 8. Thesystem of claim 3 wherein the processor is adapted to calculate theestimated position of the radiation source by identifying a line segmentbetween the closest points between a first line defined by the firstincident angle pair and the position of the first radiation sensor and asecond line defined by the second incident angle pair and the secondradiation sensor.
 9. The system of claim 8 wherein the processor isadapted to calculate the estimate position of the radiation source bybisecting the line segment.
 10. The system of any one of claims 3 to 9wherein the first and second sensors are mounted in a fixed relationshipto one another.
 11. The system of any one of claims 3 to 9 wherein thefirst and second sensors may be independently positioned relative to oneanother.
 12. A method of estimating the position of a radiation source,comprising: positioning first and second sensors in a three dimensionalspace, wherein the first second sensor are separated by a sensor spacingdistance; calculating a first line corresponding to the position of thefirst sensor and the position of the radiation source; calculating asecond line corresponding to the position of the second sensor and theposition of the radiation source; and calculating an estimated positionof the radiation source based on the first and second lines.
 13. Themethod of claim 12 wherein the position of the radiation source isestimated by identifying a point of intersection between the first andsecond lines.
 14. The method of claim 12 wherein the position of theradiation source is estimated by identifying a line segment between theclosest points on the first and second lines.
 15. The method of claim 14wherein the position of the radiation source is estimated by bisectingthe line segment.